Asthma is a disease in which bronchoconstriction, excessive mucus production, and inflammation and swelling of airways occur. This causes widespread variable airflow obstruction which makes it difficult for an asthma sufferer to breathe. Asthma is a chronic disorder, primarily characterized by persistent airway inflammation. Asthma is further characterized by acute episodes of additional airway narrowing via contraction of hyper-responsive airway smooth muscle.
Asthma is traditionally managed pharmacologically by: (1) long term control through use of anti-inflammatories and long-acting bronchodilators and (2) short term management of acute exacerbations through use of short-acting bronchodilators. Both of these approaches require repeated and regular use of prescribed drugs, which often present difficulties in patient compliance. High doses of corticosteroid anti-inflammatory drugs can have serious side effects that require careful management. In addition, some patients are resistant to steroid treatment. The difficulty of avoiding stimulus that triggers asthma is also a common barrier to successful asthma management. As such, current management techniques are neither completely successful nor free from side effects.
Presently, a new treatment for asthma is showing promise. This treatment comprises the application of energy to the airway tissue. This treatment is described in more detail in commonly assigned U.S. Pat. Nos. 6,411,852; 6,634,363; 7,027,869; 7,104,987 and U.S. Publication No. 2005/0010270, each of which is incorporated herein by reference.
The application of energy to airway tissue, when performed via insertion of a treatment device into the bronchial passageways, requires navigation through tortuous anatomy as well as the ability to treat a variety of sizes of bronchial passageways. As discussed in the above referenced patents and applications, use of a radio frequency (RF) energy delivery device provides one mechanism for treating tissue within the bronchial passageways.
FIG. 1 illustrates a bronchial tree 90. As noted herein, devices treating areas of the lungs desirably have a construction that enables navigation through the tortuous passages. As shown, the various bronchioles 92 decrease in size and have many branching segments 96 as they extend into the right and left bronchi 94. Accordingly, an efficient treatment utilizes devices that are able to treat airways of varying sizes as well as function properly when repeatedly deployed after navigating through the tortuous anatomy.
In addition to considerations of navigation and site access, there exists the matter of device orientation at the treatment site. The treatment devices generally make contact or are placed in close proximity to the target tissue. However, in utilizing the treatment devices in a patient, visibility of the energy delivery element, particularly depth perception, within the lung airways may be relatively limited as viewed from an imaging lens of an access device, such as a bronchoscope or endoscope. Limited visibility combined with a variety of other factors, including airway movement due to patient breathing, coughing, and/or wheezing (tidal motion) as well as movement of the access device, may make it difficult to ensure desired axial treatment of the lung airways with the energy delivery device.
For example, in procedures where a relatively long region of tissue is to be treated (e.g., longer than a length of the energy delivery element), difficulty in ascertaining the amount of tissue being treated may result in over-treatment of the same region or non-treatment of the target region. In particular, as the energy delivery element is translated from a first region to a second region and so on, portions of the target tissue may be over-treated or skipped entirely. Additionally, such conditions may result in slower procedures that increase total procedure time and patient discomfort.
In view of the above, methods and devices are desired for treating tortuous anatomy such as the bronchial passages which enable a user to effectively and efficiently treat tissue and relocate an energy delivery device along one or more portions of the tissue.